Threshold displacement energy and damage function in graphite from molecular dynamics

A.J Mckenna,T Trevethan,C.D Latham,P.J Young,M.I Heggie

doi:10.1016/j.carbon.2015.11.040

A.J Mckenna, T Trevethan + Show 3 more

Open Access

https://doi.org/10.1016/j.carbon.2015.11.040

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Journal: Carbon	Publication Date: Nov 22, 2015
Citations: 44	License type: cc-by

Affiliation: University of Surrey

Abstract

The environment dependent interatomic potential (EDIP) including Ziegler–Biersack–Littermark (ZBL) interactions for close encounters is applied to cascades starting from a host atom and from an interstitial atom. We find the room temperature displacement threshold to be 25 eV, increasing to 30 eV at 900 K. The latter correlates well with the measured threshold for vacancy production. Additionally, divacancy production is found to occur, including interlayer divacancies from around 60 eV. The data suggest a new, continuous damage function applies, where the threshold region depends on the square root of the primary knock-on atom (PKA) energy in excess of the threshold, evolving to a linear dependence on PKA energy.

Highlights

Graphite is a fundamental core component in present and past gas cooled nuclear reactors in the UK [1]. It may well feature in another generation of reactors (Gen IV) operating at high temperatures, which have been through a number of prototype designs, with the latest being high temperature reactorepebble module (HTR-PM), currently under construction in China
We first observe that the environment dependent interatomic potential (EDIP) threshold for graphene based on a single (001) trajectory is 20.9 eV, which is encouragingly close to the value of 22À23 eV given by ab initio calculations [23e25] and 23.6 eV from experiment [21,22]
Atomic displacement defects, such as the separated or intimate Frenkel pair (FP), and the D defect are factored into the assessment of threshold displacement energy (TDE)

Summary

Introduction

Graphite is a fundamental core component in present and past gas cooled nuclear reactors in the UK [1] It may well feature in another generation of reactors (Gen IV) operating at high temperatures, which have been through a number of prototype designs, with the latest being high temperature reactorepebble module (HTR-PM), currently under construction in China.. Atomic displacement leads to many defects, but the elementary ones are the vacancy, the (self-) interstitial and the bond switch defect. Their ground state structures obtained by Density Functional Theory (DFT) are given in Fig. 1(a) to (c), respectively, including their point group symmetries.

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